Grinding wheel



March 6, 1934. w. w. GREENWOOD GRINDING WHEEL Filed'Aug. 8, 1930 witnesses W Mace Wfircenwood 1% a @1596 I ATT NEY Patented Mar. 6, 1934 UNITED STATES PATENT OFFICE GRINDING WHEEL Application August 8, 1930, Serial No. 473,858

14 Claims.

This invention relates to grinding wheels and more particularly to a grinding wheel made up of a plurality. of abrasive segments which are mounted in an operative grinding relationship on a rotatable support.

It has been the practice heretofore in the manufacture of wood pulp grinding wheels in accordance with my prior Patent No. 1,469,723, in which a plurality of abrasive segments of ceramic bonded abrasive grains are mounted in proper grinding relation on a cylindrical support. to clamp the segments to the supporting surface by means of clamping blocks which wedgingly engage beveled shoulders formed on the adjacent segments.

In segments of this type, the clamping shoulders and bottom portions are provided with shoes which are shaped to fit the clamping and supporting surfaces. Since these segments are very brittle and weak it is necessary that they be mounted accurately and rigidly in position on the support and there held in place against movement during the grinding operation. It is desirable that the clamping and supporting shoes properly matewith the corresponding clamping surfaces of the wedge block and drum, otherwise breakage of the segments may occur due to the building up of the clamping pressure at one or more points instead of being uniformly distributed throughout the entire area of contact with the clamping surface.

Heretofore these shoes have been formed on the segments by means of master molds but owing to inaccuracies in the shape of the drum and the wedge blocks, it has been necessary to lap the parts in place to give the desired fit. This operation has involved considerable waste of time and expense. Also breakage of a segment in a wheel during use or after assembly is a serious matter and it has been necessary to return the entire wheel structure to the factory for repairs and a possible rebuilding of the wheel when such breakage occurs.

It is accordingly one object of this invention to provide a grinding wheel construction which overcomes such difliculties and which may be economically and easily manufactured, as well as readily assembled at the point of use.

A further object of this invention is to provide a segmental grinding wheel construction in which the abrasive segments are arranged on a cylindrical support in such a manner as to be independently removable and replaceable without requiring dismantling the wheel.

Another object is to provide a segmental grinding wheel construction in which each abrasive segment is adjustably mounted in a holder and properly supported therein and this holder is separately secured to the rotatable support, whereby the clamping pressure of mounting the segment on the support is not carried by the fragile abra- 0 sive material but solely by the holder.

A still further object of this invention is to provide a segmental grinding wheel construction in which the abrasive segments are accurately and rigidly mounted in holders at the correct 5 clamping pressure, each holder being adjustably mounted on the support under any desired clamping pressure, and in which the holder is of such character that it need not fit the support accurately, but may be clamped rigidly in position thereon, thus making it unnecessary to lap any of the parts into accurate contact.

With these and other objects in view as will be apparent to one skilled in the art, this invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawing in which like reference numerals indicate like parts:

Fig. 1 is a fragmentary sectional view of one 30 embodiment of the invention; and

Fig. 2 is a fragmentary perspective view showing a series of abrasive segments upon a rotatable support.

A segmental grinding wheel made in accord- 35 ance with this invention comprises a rotatable support carrying a series of abrasive segments made of suitable material, such as crystalline alumina or silicon carbide grains bonded by vitrified ceramic materials. Each of the segments is mounted within a holder and preferably in such a manner that it may be adjustably secured therein, and this holder is in turn removably clamped to the support, whereby the segments do not receive the direct clamping stresses. In such a construction the segment may be preformed to fit the holder, as by means of shoes molded on its faces and preferably against a wall of the holder used as a mold. Since the holder may be made of iron or other strong material it may be adjustably mounted on the rotatable support without necessitating any preliminary operationof fitting the two parts accurately together. This is preferably accomplished by means of clamping devices located between and wedgingly securing the holders to the support.

As illustrated in the drawing, one embodiment of this invention is shown as applied to a grinding wheel of the type shown in the patent to Greenwood No. 1,469,723, but which is of genllo eral utility in various fields. The wheel may comprise a wide faced cylindrical drum supported by a hub 11 and spokes 12 having an outer cylindrical surface 13 on which is mounted several rows of abrasive segments 14 to provide a cylindrical grinding surface 15.

In order that the segments may be removably secured to the drum so as to form an abrasive annulus, each segment is adjustably mounted within a U-shaped metal holder 1'7 and this holder is in turn adjustably and removably fastened on the drum. The segments thus secured are shaped and arranged to form a substantially continuous grinding surface. The holder is provided with inwardly converging flanges 18 on its sides having inner clamping surfaces 19 arranged to wedgingly grip the beveled clamping shoulders 20 formed on the inner dovetailed portion of the segment. The outerperipheral surface 21 of each holder is shaped to fit the curvature of the drum, and the under side of the holder has a series of bosses 22 loosely fitted into suitable recessed portions 23 formed in the supporting surface 13 of the drum which serve to roughly locate the holder in its clamping position. The segment is adjustably secured within the holder by means of adjusting screws 25, passing through the bosses, which engage the under side of a movable clamping plate 27 contacting on its upper side with the bottom of the segment. A proper adjustment of these screws will press the clamping plate firmly against the segment and force the beveled shoulders 20 of the segments upwardly and wedgingly against the corresponding beveled surfaces of the clamping flanges 18.

In order that the segments may properly fit against the flanges 18 of their holder and against the pressure plate 27 it is proposed to mold shoes 28 of suitable material, such as lead or Babbitt metal or other suitable material, on the clamping shoulders and spaced shoes 29 on the bottom of the segment adjacent to its outer corners. One simply way of insuring an accurate fit between the shoes and the associated parts within the holder is to utilize as a mold the holder. 17 and the pressure plate Z'Ilocated therein which will later be used to support any particular segment. Then by casting the shoe material between the mold parts and the segment, the shoe is caused to adhere to the segment and to fit correctly against the pressure part of the holder. To this end, each abrasive segment is placed directly in its holder in correct position for mounting, and to insure having the shoe 28 of the proper width and thickness, it is advisable to place small shoes of rubber or leather (not shown) along the segment surface which serve as temporary dams to hold the molten material in. the desired place. The segment may be positioned in the holder by movement of the clamping plate 2'7 by means of the screws to leave sufficient clearance between the segment and the holder to form a shoe of the proper thickness, after which the molten material is poured into the mold openings and allowed to harden. After i the shoes thusmade integral with the faces of the porous abrasive segment have hardened, the clamping plate 2'1 may be further tightened in order to take up any slight play caused by shrinkage of the molten material and thereby force the segment wedgingly against the clamping surfaces 19 and the flanges 18 of the holder 17, with each shoe bearing accurately and directly against that portion of the holder or the clamping plate to which it has been molded. It will be evident that various moldable materials, such as the synthetic resins, may be used for this purpose and that the operation will be varied as is understood by those skilled in the art.

In order to fasten a series of the segments and their holders in position on the drum, the outer sides of each holder are provided with a plurality of beveled clamping surfaces 30, preferably located in recessed portions 31, which are wedgingly engaged by wedge blocks 32 inserted in the space 33 between the dovetailed portions of the segments. The wedge blocks are provided with beveled faces 34 corresponding with the sloping surfaces of the recessed portions 31. Each wedge block is adjustably secured to the drum by means of bolts 35 screw threaded at their upper ends into the wedge blocks 32, the lower ends of the bolts passing through holes in the drum and secured there by the nuts 36 engaging the under side thereof. Various other constructions may obviously be employed to fasten the holders in position.

A suitable filling medium is placed in the crevices between the adjacent segments to hold the segments rigidly in position against lateral pressures tending to break them. This may be accomplished by pouring a cementitious or filling material into the crevices, but I prefer that each segment be provided with a facing adapted to fit accurately against the adjacent facing of another segment and thereby insure ready removal of the segments. For this purpose, the adjacent faces of the segments may be provided with preformed facings 38, of such materials as lead, Babbitt metal, sulfur, or resins, which may be molded thereon and have smooth surfaces 39 affording a plane contact surface adapted to fit against the adjacent segments. Such a facingis disclosed in my prior Patent No. 1,870,449. Ordinarily, it is preferred that these facings be located on each side of the segment so that the facing will engage the accurately formed facing surface on the adjacent segment; but in certain cases it is suflicient to provide but one facing in each crevice between two segments, in which case the act of clamping the segments in position will serve to draw the facing on the one segment into firm contact with the abrasive material of the adjacent segment.

It will be apparent from the, above disclosure that this invention provides a way whereby abrasive segments may be correctly mounted on a drum and in proper alignment to form a cylindrical grinding surface and individual segments replaced when desired. Moreover, the segments and their shoes are so accurately fitted to the holder that the clamping strains are distributed throughout a large area of contact. Each segment may be secured inplace under such clamping pressure as is found safe, considering the fragile nature of the material; but a high pressure may be impressed upon the holders to make sure that the segments do not move, and this clamping pressure cannot affect the fragile ceramic material of the segment. This construc- 1 tion insures that the wedge blocks will clamp the segments to the drum by engaging external clamping surfaces formed on the holder sides instead of gripping the shoulders of the abrasive, segments themselves. Such awheel may be asi sembled at the point of use and repaired easily by unskilled workmen, without necessitating the return of the wheel to the factory. In view of the above disclosure, various modifications of this in vention will be appment to one skilled in the art port, a plurality of abrasive segments arranged thereon to form a cylindrical grinding surface, holders adjustably secured on the segments which have surfaces fit'ing said support, and means for fastening the holders to the rotatable support.

2. A grinding wheel comprising a rotatable support, a series of segment holders thereon, abrasive segments having shoes fitting said holders, means for adjustably securing each segment within a holder, and means for removably securing the holders on the support.

3. A grinding wheel comprising a rotatable support, a series of segment holders thereon, abrasive segments having shoes fitting said holders, means for securing each segment within a holder, preformed facings integral with the adjacent faces of the segments and shaped to accurately fit against each other, and means for removably securing the holders on the support.

4. A grinding wheel comprising a rotatable support, a series of abrasive segments arranged thereon as an annulus, each segment having a beveled clamping shoulder, a holder having an outer surface fitting the rotatable support and an inner surface clampingly engageable with the shoulder of a segment, means for adjustably securing the segment within the holder, and means for removably securing the holder on the support.

5. A grinding wheel comprising a rotatable support, a series of abrasive segments arranged thereon as an annulus, each segment having a shoulder, a beveled clamping shoe formed on each shoulder, a series of holders arranged to be mounted on the rotatable support, each having an inner surface engageable with the shoulder of a segment, means for adjustably securing the segments within said holders, and means for removably securing the holders on the support.

6. A grinding wheel comprising a rotatable support, a series of abrasive segments arranged thereon as an annulus, each segment having a beveled clamping shoulder, a holder removably secured to each segment, said holder having a flange engaging the clamping shoulder on the segment and providing an outer beveled clamping shoulder, and means wedgingly engaging said outer shoulder on the holder and securing the latter on the support.

7. A grinding wheel comprising a rotatable support, a series of abrasive segments arranged thereon as an annulus, each segment having a beveled clamping shoulder, a holder for each seg-' ment having an inner surface clampingly engageable with the shoulder of a segment and an outer surface fitting the rotatable support, the holder having a plurality of external beveled clamping surfaces, and means wedgingly engaging said external clamping surfaces on the holder and removably securing the latter on the support.

8. A grinding wheel comprising a rotatable support, a plurality of abrasive segments arranged to form a cylindrical grinding surface, a series of holders arranged on the support, each having opposed outer beveled clamping surfaces, means for removably securing each segment on a holder, a clamping block mounted between adjacent holders and having beveled surfaces engaging the beveled surfaces on the holders, and adjustable means for securing the blocks to the support and for wedgingly and removably fastening the holders in place on the support.

9. A grinding wheel comprising a rotatable support, a plurality of abrasive segments arranged thereon to form a cylindrical grinding surface, a plurality of holders therefor arranged to be removably assembled on the support, each holder having clamping shoulders between which the segment is removably secured and adjustable means for removably clamping the segment rigidly. in position therein, and means for removably fastening the holder and the segment carried thereby to the rotatable support.

10. A grinding wheel comprising a rotatable mounted drum having a cylindrical surface, an annulus of abrasive segments arranged thereon to form a cylindrical grinding surface, each segment being provided with a pair of clamping shoulders, a holder for each segment having an outer peripheral surface shaped to fit the curvature of the drum and internal clamping portions engageable with said shoulders, means for removably and adjustably clamping each segment on a holder, means for securing the holders and the segments carried thereby on the supporting surface of the drum, and a medium filling the crevices between the adjacent faces of the segments.

11. An abrasive unit adapted to be assembled with similar units and be removably clamped on a rotatable support and form a grinding surface comprising a segment of bonded abrasive grains having an outer convex grinding surface and opposed shoulders, each shoulder being provided with beveled clamping shoes integral therewith, a holder for the segment having inner beveled clamping portions which engage said shoulders and outer beveled clamping surfaces shaped for engagement with clamps which secure the holder on the support, a shoe integral with the bottom of the segment, and a movable clamping plate adjustable within the holder for engaging said bottom shoe and wedgingly clamping the segment against said inner clamping portions of the holder.

12. An abrasive unit adapted to be assembled with similar units and be removably clamped on a rotatable support and form a grinding surface comprising a holder having an outer surface shaped to fit the rotatable support and clamping portions shaped for engagement with clamps which removably secure the holder on the support, an abrasive segment removably secured on the holder, means for removably and adjustably securing the segment on the holder, and means on the holder engageable with a portion of said support which aids in locaing the holder and the segment carried thereby in a correct clamping position on the support when mounted in an assembled wheel structure.

13. A grinding wheel comprising a rotatable support, a series of abrasive segments arranged thereon as an annulus, each segment being provided with a pair of clamping shoulders, a holder for each segment having an outer surface fitting the rotatable support and a pair of opposed side surfaces formed integrally therewith and clampingly engageable with a shoulder of the segment, means for removably securing each segment between the side surfaces of a holder, and adjustable means for drawing the-holders radially inwardly and securing them rigidly in position on the support.

14. A grinding wheel comprising a rotatable lot support, a plurality of abrasive segments arranged thereon to form a cylindrical grinding surface, each segment being removably mounted on a holder and having clamping shoes cast integral 5 therewith which are accurately shaped to fit that portion of the holder on which the segment seats 

